The move, of course, puts WhatsApp – and by extension, Facebook – in direct competition with established VoIP companies such as Skype, with its 31 million-plus regular user base. But it will also help expand the appeal and footprint of WhatsApp, long a stated aim of the California company.

"Our team has always believed that neither cost and distance should ever prevent people from connecting with their friends and loved ones, and won’t rest until everyone, everywhere is empowered with that opportunity," Koum wrote last week, in a blog post announcing the acquisition by Facebook.

In related news, in a separate speech at MWC, Facebook CEO Mark Zuckerberg defended the size of the $19 billion acquisition. In fact, he said, citing the half billion WhatsApp users, the platform was probably worth even more than that. (WhatsApp says it is adding new users at a pace of millions a week; as Karis Hustad of the Monitor recently noted, the platform is particular popular in emerging markets.)

"It's on a path to connecting a billion people," Mr. Zuckerberg said. "There are very few services in the world that can reach that level and they're all incredibly valuable."